This invention relates to fuel injection pumps for internal combustion engines, and more particularly to a lubricating oil feeding device for use with such injection pump, which is capable of avoiding clogging of its lubricating oil feeding passage with sludge or the like contained in the lubricating oil.
An in-line type fuel injection pump used in general in Diesel engines is constructed such that each of the plungers has its lower end disposed in contact with a tappet via a lower spring seat on which a plunger return spring is seated, and the tappet has a roller disposed in camming engagement with the camming peripheral surface of a camshaft rotatable in synchronism with rotation of the output shaft of an engine associated with the pump. With this arrangement, as the camshaft rotates, the plunger is reciprocatingly moved within its plunger barrel to carry out suction and delivery of fuel.
The camshaft is accommodated within a cam chamber which is supplied with lubricating oil to lubricate sliding parts such as the camshaft and its peripheral parts. A conventional lubricating oil feeding arrangement is such that a lubricating oil feeding bore is formed in the pump housing, which opens in a bore in which the tappet slides so that lubricating oil fed into the bore is delivered into the cam chamber through a clearance between the inner wall of the bore and the tappet. The sliding motion of the tappet prevents clogging of the lubricating oil passage with sludge or a like substance in the lubricating oil, which permits setting the interior diameter of the lubricating oil passage at a desired value so as to enable the supply of lubricating oil at a moderate flow rate.
However, there may be a case where the lubricating oil feeding bore cannot be provided in the peripheral wall of the bore in which the tappet slides, depending upon the configuration of the fuel injection pump applied, the shape or size of the space in which the pump is to be mounted, etc. In such case, it has conventionally been employed to form a lubricating oil feeding bore in the peripheral wall of the cam chamber to supply lubricating oil directly into the chamber. According to this method, the interior diameter of the lubricating oil feeding bore has to be set at a large value so as to avoid clogging of the bore with sludge or the like. As a consequence, an excessive amount of lubricating oil can be supplied to the injection pump so that the plunger sucks part of the lubricating oil in the pump and delivers it together with fuel.